Electric machine



Feb.` 20, 1940.

E. scHAl-:REN 2,190,887

ELECTRIC MACHINE Filed Feb. l0, 1938 MMM Patented Feb. 20, 1940 l UNITED STATES PATENT OFFICE ELECTRIC MACHINE Application February 10, i938, serial No. 189,839

` En Switzerland February 12, 1937 8 Claims.

The present'` invention relates to dynamoelectric machines for radio telegraphy and telephony, and more particularly, to armatures oi such machines provided with a plurality oi wind" ings forming parts of electrically independent circuits. y

With known plural circuit machines high iren quency disturbances of the potential which may arise in the conductors of one of the circuits on K9 the armature, e. g., through sparking at the collector, also cause similar disturbances in the adjacent conductors of others of the said circuits, on account of the electrostatic interaction between the said conductors.

l5 Although in general applications oi dynamon electric machines such high frequency disturbances are not a severe drawback they are very undesirable in machines employed for purposes v of radio telegraphy and telephony. With these,

5*" it is necessary to connect smoothing means, in

the form of iilters, to the circuit where the disturbances are likely to be felt.

In the known electric machines oithe kind to which the invention relates, the smoothing T7 means connected to each one of the several circuits must not only be constructed for eliminating the high frequency disturbances which have their origin in the circuit itself, but also for eliminating disturbances having origin in other fifi circuits which have conductors carried by the same armature, so that .their disturbances are electrostatically transmitted to the circuit in question. Thus, rather bulky or complicated smoothing devices are required, even in connec- R tion with circuits not likely to cause such dis-- turbances.

One of the purposes of the present invention is to provide an eiiective electrostatic shielding between the windings oi different circuits, so

u that the potential in each circuit is subject only to such variations as have their origin in the circuit itself.

Further, the invention has for its object to Y provide for a convenient arrangement of such if shielding means on the rotating armatures oi dynamo-electric machines.

Another important purpose of the invention. is to provide such an arrangement of the shielding m means as 'to prevent the formation of undesir able eddy currents (Foucault currents) therein. The main object of my invention is, therefore, to provide means for preventing the electrostatic eld associated with the currents in one 55 of said circuits from influencing the currents in other of said circuits,that is, to prevent high frequency interference.

Further objects and advantages of my invention will appear from the following description oi an embodiment thereof with reference to the accompanying drawing, and it will be understood that while I have described what may be considered as a preferable embodiment oi my invention, I do not limit myself to the precise conl ditions or proportions herein set forth, as they may be varied by those skilled in the art in accordance with the particular purposes for which they are intended, and the conditions under which they are to be utilized. d

In the accompanying drawing, L

Fig. l shows in longitudinal section a generator machine designed for supplying electric current at two different potentials. Such generator machines are used, by way of example, for purposes of wireless telegraphy. fio

Fig. 2 is a cross-section on the line A-A ci Fig. 1, showing at a larger scale the arrangement of the parts within the slots of the armature. I

The cylindrical housing il of the generator JIS machine is tt'ed with end plates 2 and 3 in which bearings are provided for supporting the armature shaft l; at its end 4, the latter is coupled to driving means not shown in the drawing. 5 and 6 lare commutators of usual conil() struction consisting each of a number of bars fastened tothe shaft and insulated therefrom and from each other.

'I'he commutator 5 cooperates with a carbon brush 5l which is guided in an insulated brush 353 holder 52, and with another carbon brush 53, which is guided in a brush holder 55 integral with the end plate 2. Each one of the said carbon brushes is resiliently pressed onto the sur-- face of the commutator 5 by a spring 55. The l? brush 5| is electrically connected to an ina sulated terminal 56, whilst the brush 53 is grounded through the end plate 2, as indicated diagrammatically at 51. However, the said brush 5l is also connected to grounded terminal 53. One consumer circuit vmay be connected be-l tween the terminals 5'5 and 58.

Similarly, aV carbon brush Bl guided in the insulated brush holder t2 connected to terminal it and a carbon brush 53 guided in the grounded brush holder 64 connected to the grounded terminal 58 are provided on the end plate 3 for cooperating with the` commutator 6, onto which they are pressed by springs 65. The second con- 35,

tucked up over the winding head 1S.

sumer circuit may be connected between the said terminals 66 and 68.

rIn the housing 4I exciting means are provided n consisting of stationary armatures 42 and 43 and of field coils 44 and 45 which latter are connected in series to one another between the terminals 53 and 58, thus shunting the armature winding I8 hereinafter referred to.

Between the commutatore 5 and 6 the shaft I carries an armature core 'l built up from iron discs located between end plates 8 and 9 of insulating material. Between the latter and the commutatore 5 and 6 metallic drums IIJ and EI are fastened to the shaft I. Both said drums and the iron discs forming the core l are electrically connected to the ground, through the shaft i and the end plates f2` and 3. The core 'l has slots of trapezoidal cross-section extending parallel to itsl axis along its outer surface and communicating with the latter through longitudinal openings. A

Each of said grooves is entirely lined with a strip I2 of insulating board. For a small portion of the slots length at its end facing the commutator 5 a narrow strip `I3 of tin-foilis placed over the board I2 at the bottom of the slot. The ends of said tinfoil strips project from the ends of all slots and are maintained in electric contact with the drumdil by means of a `band of insulating boardwound across them and around said drum. Strips I6 of tin-foil, which are of U-shaped cross-section in their primitive form, are lodged in the slots on the insulating board lining I2 and on the inner ends of the tin-foil strips lf3 with which they are in conducting contact. The strips l5 are lined with corresponding strips Il' of silk tissue.

The insulated copper wire conductors I8 of one of the windings are Wound into the slots thus lined. Each of them runs from one bar of the commutator 5 through one slot ofthe core 'I to the head I3 of the winding and thence through another slot and through the head back to the beginning of the iirst-mentioned slot. After several such turns the conductor joins another barA of the commutator 5. The longitudinal edges of the silk strip I'I, and with them those ofthe tin-foil strip i6, are folded down so as to'overlap each other on the conductors thus Wound into each slot and they are covered with a strip 2| of insulating board which projects from the core end plate 9, for the purpose hereinafter to be explained. A band 22 of tin-foil is wound around the outside of the-drum Il, said band being much broader than the drum. Its projecting portion is dividedinto lobes 23 by cuts carried in diametral' planes. Between the band 22 and the head |9- of the conductors a silk ribbon 24 is interposed, the latter being also much broadery than 'the drumv II. The lobes 23 and lthe corresponding portion of the ribbon 2li are Their edges rest around the `latter on the projecting ends of the strips 2l so that the lobes 23 are insulated from the `tinfoilstrips Iii. The ends of said lobes are covered'by a further tin-foil strip 25 and an insulatingboard strip 2t wound all around and across them.

The outer surface of the winding head 2] is covered by a silk ribbon 2l, by a tin-foil band 28 carried in electric contact across the projecting ends of the tin-foil strips l5, and by a band `29 of insulating board.

On the described coverings of the conductors I8 of the said winding,- the winding. of a second circuit is lodged in the same slots. This winding consists of conductors 30 connected to the bars of the commutator t, which conductors are Wound to coils, comprising bundles of conductors Wrapped into silk tissue and secured by bandages before being inserted into the armature slots. In the present example, this second Winding has no metallic envelope. A further strip of insulating board is placed in each slot upon the conductors of said second Winding. All the conductors and their wrapping are maintained in place by wooden key bars 32.

The heads 33 of the second winding are protected by pieces 34 of impregnated fabric fastened by cord bindings 35. On the fabric 34 there are also wire bindings Sii by means of which the headsof all windings and the fabric, tin-foil, bands of insulating board inserted between them are pressed together and secured against centrifugal force. other suitable material are provided beneath the wire vwindings 36 to prevent them from cutting into the fabric.

When the armature shaft I is rotated, an alternating electromotive force is set up in opposite bars of the commutator 5 through induction in the conductors I8. As in dynamos of usual type this electromotive force is commutated into a direct current from brush 5I 4to the terminal 55, thence through' the first consumer circuit to grounded terminal 53, and back to brush 53. Simultaneously, the excitingrcoils land 45, which are connected between .the term minals 56 and 58, arey energized, whereby the magnetic field exciting the machine is obtained. The force lines of said field go from the stationary armature core 32 through the rotary armature core l, the opposite stationary arma-l ture core 43 and back through the housing M. A direct current is alsoobtained by commutation of the current induced in the conductors 363 of the second armature winding, the direct cur- Bands 'i8 of metal or rent going from brush 6I and terminal 35 through the second consumer circuit and back to grounded terminal 68 and brush 63.

The described shielding of the conductorsk i8 of the rst winding by Jmeans of the tin-foils I6, 22, 23, 25 and 28 all electrically connected to the drums IU and I! which are grounded and thus remain at a substantially constant potential, serves to maintain the electrostatic field in the conductors I8 substantially unaffected by disturbances of the electrostatic field around the conductors 33. Such disturbances may, for example, arise from sparking at the commutator ii. When the armature'is rotated in the magnetic field set up by the exciting means, the induction of short-circuit currents in the tin-foils is prevented as far as possible, because the said foils and their connections do knot form loops encircling the magnetic flux whichvaries substantially when the armature is rotated about its axis.

'Ilo avoid the formation of such loops, the tinoils 22/23 and IS are insulated from each other though both are electrically connected to the shaft I, the former through the drum il, and the other through the strips I3 and the drum It. The' strip 25 communicates with the ground or constant potential body only through. lobes 23 of the band 22. On the other hand, vthe band 28 has a plurality of connections to the drum IG, each across the end portion of a strip I6 and along one of the strips I3; each-two such connections, together. with the intermediate portions of the band 2t and of the drum I0, form a conducting loop. However, these loops do extend only very little in a direction parallel to the armature axis, so that, when the armature is rotated, the magnetic liux encircled by them varies only by a small amount in comparison with the total flux crossing the armature.

The overlapping longitudinal edges of each strip I6 are in conducting contact with each other, so that each of the said strips forms a closed conducting circuit around thel conductors I8. These circuits being perpendicular to the axis of rotation ofthe armature, the flux encircled by them does not vary when the armature is rotated.

The armature construction according to the invention is suitable for rotary converters as well as for generators, and may be applied to any type of dynamo-electric machine of appropriate type especially where employed in radio telegraphy or telephony.

What I claim is:

l. In a dynamo-electric machine in combination a core having slots formed therein, a plurality of electrically independent sets of conductors carried on said core, said sets of conductors being adapted for connection to independent circuits and for operation at materially diierent potentials, each conductor having portions located outside said slots, and electrically conducting shielding members interposed between such portions of the said conductors. of different sets as are located outside said slots.

2. In a dynamo-electric machine in combination a core having slots formed therein, a body adapted to persist at substantially constant electric potential, a plurality of electrically independent sets oi conductors carried on said core, portions of conductors of diiierent sets being lodged in the same slots of said core, electrically conducting shielding members interposed in such slots of said core between the said conductors of diiierent sets and each insulated from said core and from shielding members interposed in other slots of said core, said shielding members being each separately connected to said body.

3. In a ldynamo electric machine in combination exciting means ior producing a magnetic field when energised, a core movable relatively to said exciting means, a body adapted to persist at substantially constant electric potential, a plurality of electrically independent sets of conductors carried on said core, electrically conducting shielding members interposed between the Said conductors of diilerent sets, a plurality of conducting members electrically connected at their one end to the same one of said shielding members and at their other end to the said body, the loops formed by such shielding member together with two of said conducting members connected to the shielding member and said body being so arranged in relation to said core that when the latter is' moved with said exciting means energised, the variation of the magnetic flux encircled by said loops is small in comparison to the total magnetic flux produced by said exciting means.

4. In a multiple-circuit dynamo-electric machine for radio telegraphy and telephony in combination a body of substantially constant electric potential, a core, a plurality of electrically in dependent sets of conductors Wound on said core so as to cover a portion only of its surface, electrically conducting shielding members interposed between the said conductors of different sets and between the conductors of at least one set and the said core, each of the said shielding members slots of said core between the said conductors of different sets, and between the conductors of at least one set and the said core, each of said shielding members being insulated from direct contact with said core and said conductors and having one end separately connected to the saidv body, the other end being free of any electrical contact or connection.

6. In a multiple-circuit dynamo-electric machine for radio telegraphy and telephony, a substantially cylindrical transversely laminated core having longitudinal slots, a body of substantially constant potential, a lining of insulating material in each of said slots, a longitudinally extending shielding strip of metal foil in each oi said slots and having its one end electrically connected to said body, said shielding strip being arranged on said lining so as to be insulated from direct contact with said core, a set of insulated conductors arranged on said core in the form of bundles carried each in one of such slots, and each of the said shielding strips having its longitudinal edges joined on one of the said bundles so as to form a tube therearound, a second set oi conductors electrically independent from the conductors of the said iirst set, the conductors of this second set being arranged on said core so as to have portions lodged within the said slots but outside of the tubes constituted by the said shielding strips.

7. In a multiple-circuit dynamo-electric machine for radio telegraphy and telephony in combination a core having slots formed therein, a plurality of electrically independent sets of conductors carried on said core, each conductor having portions carried in said slots and connecting portions located outside said slots at each end of the said core, electrically conducting shielding members interposed at each end of the said core between the whole of the connecting portions of the conductors of one set and the Whole of the connecting porti-ons of the remaining conductors at the same end of the said core.

8. In a multiple-circuit dynamo-electric machine for radio telegraphy and telephony means for providing a directed magnetic field, a core rotatable in the magnetic eld provided by said means about an axis substantially perpendicular to the main` axis of the field, a body of substantially constant electric potential, a plurality of electrically independent sets of conductors carried on said core, an electrically conducting shielding member interposed between the said conductors of di'erent sets, a plurality of electric connections between the said shielding member and the said body, said connections extending in a direction parallel to the axis of rotation of the core for so short a distance that, When the said core rotates, substantially no current is induced in the circuit formed by said body through one of the said connections to the said shielding member and thence back to the main body through another of the said connections.

ERNST SCHAEREN. 

